Calcium-dependent nitric oxide production is involved in the cytoprotective properties of n-acetylcysteine in glycochenodeoxycholic acid-induced cell death in hepatocytes

The intracellular oxidative stress has been involved in bile acid-induced cell death in hepatocytes. Nitric oxide (NO) exerts cytoprotective properties in glycochenodeoxycholic acid (GCDCA)-treated hepatocytes. The study evaluated the involvement of Ca2+ on the regulation of NO synthase (NOS)-3 expression during N-acetylcysteine (NAC) cytoprotection against GCDCA-induced cell death in hepatocytes. The regulation of Ca2+ pools (EGTA or BAPTA-AM) and NO (l-NAME or NO donor) production was assessed during NAC cytoprotection in GCDCA-treated HepG2 cells. The stimulation of Ca2+ entrance was induced by A23187 in HepG2. Cell death, Ca2+ mobilization, NOS-1, -2 and -3 expression, AP-1 activation, and NO production were evaluated. GCDCA reduced intracellular Ca2+ concentration and NOS-3 expression, and enhanced cell death in HepG2. NO donor prevented, and l-NAME enhanced, GCDCA-induced cell death. The reduction of Ca2+ entry by EGTA, but not its release from intracellular stores by BAPTA-AM, enhanced cell death in GCDCA-treated cells. The stimulation of Ca2+ entrance by A23187 reduced cell death and enhanced NOS-3 expression in GCDCA-treated HepG2 cells. The cytoprotective properties of NAC were related to the recovery of intracellular Ca2+ concentration, NOS-3 expression and NO production induced by GCDCA-treated HepG2 cells. The increase of NO production by Ca2+-dependent NOS-3 expression during NAC administration reduces cell death in GCDCA-treated hepatocytes.